Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -677,6 +677,25 @@
     CLANG_REPOSITORY_STRING
     CMAKE_MAKE_PROGRAM)
 
+  set(COMPILER_OPTIONS
+    -DCMAKE_CXX_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++
+    -DCMAKE_C_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
+    -DCMAKE_ASM_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang)
+
+  if(BOOTSTRAP_LLVM_BUILD_INSTRUMENTED)
+    set(PGO_DEP llvm-profdata)
+    set(PGO_OPT -DLLVM_PROFDATA=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-profdata)
+  endif()
+
+  if(LLVM_BUILD_INSTRUMENTED)
+    set(PGO_DEP generate-profdata)
+    set(PGO_OPT -DLLVM_PROFDATA_FILE=${CMAKE_CURRENT_BINARY_DIR}/utils/perf-training/clang.profdata)
+    set(COMPILER_OPTIONS
+      -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
+      -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
+      -DCMAKE_ASM_COMPILER=${CMAKE_ASM_COMPILER})
+  endif()
+  
   if(TARGET compiler-rt)
     set(RUNTIME_DEP compiler-rt)
   endif()
@@ -703,7 +722,7 @@
   endforeach()
 
   ExternalProject_Add(${NEXT_CLANG_STAGE}
-    DEPENDS clang ${LTO_DEP} ${RUNTIME_DEP}
+    DEPENDS clang ${LTO_DEP} ${RUNTIME_DEP} ${PGO_DEP}
     PREFIX ${NEXT_CLANG_STAGE}
     SOURCE_DIR ${CMAKE_SOURCE_DIR}
     STAMP_DIR ${STAMP_DIR}
@@ -715,11 +734,9 @@
                 -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}
                 ${CLANG_BOOTSTRAP_CMAKE_ARGS}
                 ${PASSTHROUGH_VARIABLES}
-                -DCMAKE_CXX_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++
-                -DCMAKE_C_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
-                -DCMAKE_ASM_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
-                -DCLANG_STAGE=${NEXT_CLANG_STAGE}
-                ${LTO_LIBRARY} ${LTO_AR} ${LTO_RANLIB} ${verbose}
+                 -DCLANG_STAGE=${NEXT_CLANG_STAGE}
+                ${COMPILER_OPTIONS}
+                ${LTO_LIBRARY} ${LTO_AR} ${LTO_RANLIB} ${verbose} ${PGO_OPT}
     INSTALL_COMMAND ""
     STEP_TARGETS configure build
     ${cmake_3_4_USES_TERMINAL_OPTIONS}
Index: cmake/caches/PGO-stage1.cmake
===================================================================
--- /dev/null
+++ cmake/caches/PGO-stage1.cmake
@@ -0,0 +1,17 @@
+set(CMAKE_BUILD_TYPE RELEASE CACHE STRING "")
+set(CLANG_ENABLE_BOOTSTRAP ON CACHE BOOL "")
+set(LLVM_BUILD_EXTERNAL_COMPILER_RT ON CACHE BOOL "")
+
+set(LLVM_TARGETS_TO_BUILD X86 CACHE STRING "")
+set(BOOTSTRAP_LLVM_BUILD_INSTRUMENTED ON CACHE BOOL "")
+set(CLANG_BOOTSTRAP_TARGETS
+  stage3
+  generate-profdata
+  stage3-check-all
+  stage3-check-llvm
+  stage3-check-clang
+  stage3-test-suite CACHE STRING "")
+
+set(CLANG_BOOTSTRAP_CMAKE_ARGS
+  -C ${CMAKE_CURRENT_LIST_DIR}/PGO-stage2.cmake
+  CACHE STRING "")
Index: cmake/caches/PGO-stage2.cmake
===================================================================
--- /dev/null
+++ cmake/caches/PGO-stage2.cmake
@@ -0,0 +1,9 @@
+set(CMAKE_BUILD_TYPE RELEASE CACHE STRING "")
+set(CLANG_ENABLE_BOOTSTRAP ON CACHE BOOL "")
+set(LLVM_BUILD_EXTERNAL_COMPILER_RT ON CACHE BOOL "")
+
+set(CLANG_BOOTSTRAP_TARGETS check-all check-llvm check-clang test-suite CACHE STRING "")
+
+set(CLANG_BOOTSTRAP_CMAKE_ARGS
+  -C ${CMAKE_CURRENT_LIST_DIR}/PGO-stage3.cmake
+  CACHE STRING "")
Index: cmake/caches/PGO-stage3.cmake
===================================================================
--- /dev/null
+++ cmake/caches/PGO-stage3.cmake
@@ -0,0 +1,2 @@
+set(CMAKE_BUILD_TYPE RELEASE CACHE STRING "")
+set(LLVM_BUILD_EXTERNAL_COMPILER_RT ON CACHE BOOL "")